Amother and her child were taken to hospital over the weekend when both became ill with suspected meningitis.
Although the youngster attends the Brighton Health Care NHS Trust nursery at Sussex House, Brighton, the woman's other child attends the Sunshine Nursery in Eastern Road, Brighton, which suffered an outbreak of meningitis last week.
Atwo-year-old from the nursery died at Guys Hospital in London last week.
Another child from the nursery and another parent connected with it are still in hospital.
East Sussex, Brighton and Hove HealthAuthority says the five linked cases in Brighton are the largest outbreak of the highly-contagious C strain they have dealt with.
Elsewhere in the county, two students are being treated for unrelated cases of the disease.
The pupils, one from the Eastbourne College of Art and Technology, the other studying at Hastings College of Arts and Technology, were taken ill last week.
The Eastbourne youngster, who is studying for A-levels and GCSEs, is being treated at Eastbourne District General Hospital.
In Hastings, the student is being treated at the Conquest Hospital.
Dr Graham Bickler, director of public health for the health authority said: "The escalation of incidents over the weekend meant we had to take urgent action.
"As soon as the suspected cases were reported and the link between the two nurseries became apparent, we started to contact close family and friends of the children at the Sunshine nursery who were concerned.
"With a single outbreak we vaccinate immediate family and kissing contacts of those affected but with an extraordinary case like this, with five linked cases, we had to go much wider.
"We have never witnessed an outbreak like it in East Sussexand we are confident that everyone who needs to be vaccinated has been contacted."
Dr Angela Iversen, consultant in communicable disease control at East Susses, Brighton and Hove Health Authority, said: "The virulent C strain seems to spread more quickly."
Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.
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